1. School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea;
2. Atmospheric Chemistry Division, NCAR, 1850 Table Mesa Drive, Boulder, CO 80305, USA;
3. NASA Langley Research Center, MS 401A, Hampton, VA 23681-2199, USA;
4. Department of Atmospheric Sciences, University of Washington, Box 351640, Seattle, WA 98195, USA;
5. Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Sankyuk-dong, Book-gu, Taegu, Korea;
6. Stratospheric Research Group, Institute for Meteorology, Free University Berlin, D-12165 Berlin, Germany